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it is never endding history....after replaced chip was not working yet, so osciloscope on hand and checked signal from car, made a simulator signal circuit based on NE555 and studied the tacho circuit board. there was a resistor missing on circuit regarding LM1819 Datasheet, I installed adjustable resistor and made calibration helped by osciloscope and NE555. now is working fine. the tacho board with 1M adjustable resistor on it